1、Report No. 46 A Technical ReportonApril 1996 Transmission PerformanceStandards Issues Regardingthe Introduction of ATMTechnology into NetworksSupporting VoicebandServicesPrepared byT1A1.7Working Groupon Signal Processing andNetwork Performance forVoiceband ServicesCommittee T1 is sponsored by the Al
2、liance for Telecommunications Industry SolutionsAccredited by the American National Standards InstituteCopyright 1996 by Alliance for Telecommunications IndustrySolutionsAll rights reserved.No part of this publication may be reproduced in any form,in an electronic retrieval system or otherwise, with
3、out theprior written permission of the publisher.A Technical Report onTRANSMISSION PERFORMANCE STANDARDSISSUES REGARDING THE INTRODUCTION OFATM TECHNOLOGY INTO NETWORKSSUPPORTING VOICEBAND SERVICESABSTRACTThis Technical Report assesses whether industry transmission standards areadequate to support t
4、he introduction of ATM technology into networks supportingvoiceband services. In those instances where it was identified that industrystandards are inadequate, this document identifies the areas where standardswork is required to allow for an orderly integration of ATM technology, e.g.multiplexers a
5、nd switches, into the PSTN and other networks.Document T1A1.7/95-042r7Prepared byT1A1.7Working Group on Signal Processing and Network Performance forVoiceband ServicesiTRANSMISSION PERFORMANCE STANDARDS ISSUES REGARDING THEINTRODUCTION OF ATM TECHNOLOGY INTO NETWORKS SUPPORTINGVOICEBAND SERVICESEXEC
6、UTIVE SUMMARYThis document has identified that an insufficient set of transmission standards exists toprovide guidance to equipment manufacturers on how to build ATM technology whichcan be used to carry existing voiceband services and which can be gracefullyintegrated into the current networks used
7、to support voiceband based services. Inparticular this technical report has identified that study by the industry is underway formany of the parameters associated with the various ATM applications identified.However, for the local exchange and the PBX application many key parameters need tobe agreed
8、 upon because the introduction of ATM causes interaction with analog anddigital performance parameters.iiiiiTABLE OF CONTENTS1. Scope, Purpose and Application. 12. Definitions. 13. References . 34. Operating Arrangements Considered . 34.1 ATM Technology As A Digital Signal Processing Unit . 44.2 ATM
9、 Technology As A Multiplexer. 44.3 ATM Technology As A Transport System 54.4 ATM As A Switched Network Function 54.5 ATM Interworking Function (ATM Cell - PDH/SDH interworking function) . 65. Discussion 66. Matrix of Parameters vs Network Element Function Public Networks; and Wireless Networks.The p
10、urpose of the report is to promote industry awareness of the need fortransmission standards that are required to enable future integration of ATM as a partof the integrated network fabric. The report is also intended to assist program plannersof standards bodies in developing future work plans. Manu
11、facturers are expected tobenefit from this report as it highlights those areas where industry agreements arerequired to support development of compatible equipment capable of operating on anational and global basis without the need for an interworking function.The approach used in the development of
12、 this report was to identify the transmissionperformance parameters for which specification are required to facilitate the gracefulintegration of ATM technology into the digital PSTN and other networks.In this report ATM is always assumed to be riding on a physical layer standard, e.g.SONET (Synchro
13、nous Optical NETwork) or DS3. As appropriate, the report identifiesthe transmission issues that must be addressed if ATM technology is to be integratedinto the digital PSTN.In todays competitive environment with the presence of many competing carriers thereis difficulty in defining the term digital
14、PSTN. To overcome this hurdle, the termPlesiochronous Digital Hierarchy/Synchronous Digital Hierarchy (PDH/SDH) orientednetworks will be used, the intention being that these networks represent the bytedomain while ATM networks represent the cell domain. To work between thesedomains, viz. between the
15、 PDH/SDH and the ATM cell domain, it is understood that aninterworking function must exist and while it may physically occur in the PDH/SDH orthe ATM cell-oriented hardware, it is always deemed to occur at the boundaries of thePDH/SDH and ATM cell networks.2. DefinitionsAsynchronous Transfer Mode (A
16、TM)The term applied to a technology that is based on the premise that information istransported in cells. Specifically, in this document ATM is used to apply to technologythat uses ITU-T Recommendation I.361 B-ISDN ATM Layer Specification for ATM cellTECHNICAL REPORT NO. 462size and makeup, viz. 53
17、octets per cell with 5 octets allocated for the header and 48octets allocated to carry payload information.ATM Digital Signal Processing FunctionThe term applied to ATM technology that operates with cell-based signals operatingover standard line rates on both the inputs and the outputs, e.g. DS3 on
18、the input andDS3 on the output, and which modifies the payload contents of the cells as they passthrough in some prescribed manner. This device may modify none, some, or all of thecells that pass through it. This cell modification is intended to change the transmissioncharacteristics of the signals
19、in the virtual connections, e.g. this device may performecho cancellation or speech compression on some or all the virtual connections thatpass through it.ATM Multiplexer/CrossconnectThe term applied to a cell-multiplexing device that operates with cell-based signals andover standard line rates on a
20、ll interfaces, e.g. DS1 and DS3, and which passes thecells received on an input to an output. The relationship between input and output, i.e.the virtual circuits routing, does not change on a per call basis, i.e. only permanentvirtual circuits are supported. This device does not allow blocking or si
21、gnalcompression.ATM Transport SystemThe term applied to a transport system that is composed of a carrier system terminatedby an ATM multiplexer at each end. The relationship between input and output, i.e.virtual circuits, cannot change on a per call basis, i.e. permanent virtual circuits only aresup
22、ported. This device does not allow blocking or signal compression.ATM Switch (Digital Interfaces Only)The term applied to ATM technology that operates with cell-based signals and overstandard line rates on both the inputs and the outputs, e.g. DS1 on the input and DS3on the output, and which passes
23、the cells received on the input to the output. Therelationship between input and output, can change on a per call basis, i.e. switchedvirtual circuits must be supported and permanent virtual circuits may be supported.This device allows blocking and performs concentration.ATM Switch ( Analog and Digi
24、tal Interfaces)The term applied to ATM technology that operates with analog 2-wire interfaces1andstandard digital line rates on both the inputs and the outputs, e.g. DS1 on the input andDS3 on the output, and which passes the cells received on the input to the output. Therelationship between input a
25、nd output, can change on a per call basis, i.e., switchedvirtual circuits must be supported and permanent virtual circuits may be supported.(For the purposes of this document it is assumed that the cell formation function1This configuration is not intended to exclude analog 4-wire interfaces. Howeve
26、r, theintended focus is on the 2-wire interface.TECHNICAL REPORT NO. 463associated with an analog input is performed before the switch function occurs.However, this definition is not intended to constrain technical implementations.) Thisdevice allows blocking and concentration. The switch function i
27、s also required toperform 2-wire to 4-wire conversion as well as A/D conversion.ATM Interworking Function (With Narrowband Services in the PDH/SDH ByteOriented Domain)The term applied to a technology device that allows ATM systems, i.e. cell-orientedsystems, to interwork with narrowband, byte orient
28、ed systems. Although interworkingwill have to occur in both the transmission plane and the signaling plane, this documentwill restrict itself to the transmission plane.3. ReferencesThe following recommendations and standards have been referenced in this documentand are understood to contain material
29、 that would be helpful in providing guidanceduring the process of generating industry agreements associated with ATM hardware.The latest version of the recommendations or standards should be used.ITU-T Recommendation G.113 (1996), Transmission impairmentsITU-T Recommendation G.114 (1996), One-way tr
30、ansmission timeITU-T Recommendation G.122 (1993), Influence of national systems on stability talkerecho in international connectionsITU-T Recommendation G.126 (1993), Listener echo in telephone networksITU-T Recommendation G.131 (1988), Stability and echoITU-T Recommendation G.132 (1988), Attenuatio
31、n distortionITU-T Recommendation G.712, (09/92) Transmission performance characteristics ofpulse code modulationITU-T Recommendation Q.552, (1994) Transmission characteristics at 2-wire analogueinterfaces of digital exchangesANSI T1.506-1990, Network Performance Transmission Specifications for Switc
32、hedExchange Access NetworkANSI T1.508-1992, Network Performance Loss Plan for Evolving Digital Networks4. Operating Arrangements ConsideredIn the definition section a number of functions were identified, e.g. digital signalprocessing function and a multiplexer function. In this and subsequent sectio
33、ns thesefunctions are considered packaged on a one per black box basis. As a result thefunction is deemed to operate on a standalone basis and this is the way they aretreated in a matrix table in Section 6. However, in reality, more than one function couldappear in a device. For these cases, the app
34、ropriate columns from the matrix table inSection 6 should be used. The reason for identifying the function of ATM as a digitalsignal processing unit is to focus discussion on the interfaces which exist on both sidesof this ATM device.TECHNICAL REPORT NO. 4644.1 ATM Technology as a Digital Signal Pro
35、cessing UnitAn illustration of ATM technology acting as a digital signal processing unit is shown inFigure 4.1. This category is intended to include devices which may be used to performecho control functions.ATM Over a StandardBit Rate Signale.g., DS3ATM Over a StandardBit Rate Signale.g., DS3This d
36、evice may have morethan one input and one output,and the input and output ratescan be different.Note:Figure 4.1 ATM Technology Operating as a Digital Signal Processor4.2 ATM Technology as a MultiplexerAn illustration of ATM technology acting as a multiplexer is shown in Figure 4.2. Thereason for ide
37、ntifying the function of ATM as a multiplexing system is to focusdiscussion on the interfaces which exist on both sides of the ATM device. Thiscategory is intended to include devices which may be used to perform a digital crossconnect function.ATM Over a StandardBit Rate Signale.g., DS1, DS3ATM Over
38、 a StandardBit Rate Signale.g., DS1, OC3.Figure 4.2 ATM Technology Operating as a MultiplexerTECHNICAL REPORT NO. 4654.3 ATM Technology as a Transport SystemAn illustration of ATM Technology acting as a transport entity is shown in Figure 4.3.This is intended to address the situation where ATM multi
39、plexers are used inconjunction with a transport system, e.g. when ATM multiplexers are combined withSONET to provide a transport function which has DS1 interfaces. Note that thesupported service can be any rate below the DS1 rate. In this configuration the ATMmultiplexer uses permanent virtual circu
40、its which have constant bit rate channels andthus a signal compression function is not performed. For the purposes of this report, amultiplexer is defined as a device whose payload output is equal to the sum of theinputs plus overhead.ATM Over a StandardBit Rate Signale.g., DS1, DS3ATM Over a Standa
41、rdBit Rate Signale.g., DS1, DS3.Line TransmissionSystem Operatingat a Standard Ratee.g., DS3, OC3ATM Technologyas a MultiplexerATM Technologyas a MultiplexerFigure 4.3 Atm Technology Operating as a Transport System4.4 ATM as a Switched Network FunctionATM technology can operate as a switch. Figure 4
42、.4 shows this switch configured withdigital interfaces only. This figure is intended to apply to switches that could assumethe functions of a PBX, an end office, or a tandem office.Figure 4.5 shows the switch with 2 wire analog interfaces, intended to terminate astandard 2 wire telephone set on a lo
43、op access facility in the PBX or networkenvironment. This figure is also intended to apply to those cases where the ATMswitch could terminate a digital loop subscriber carrier system.This report is not intended to promote particular operating configurations, but rather isfocused on determining if st
44、andards exist for all operating arrangements.ATM Over DigitalFacilities Operatingat a Standard Bit Ratee.g., DS1, DS3ATM Over DigitalFacilities Operatingat a Standard Bit Ratee.g., DS1, DS3.Figure 4.4 ATM Technology as a Switch - Digital Interfaces Only(PBX, Local Exchange, Tandem)TECHNICAL REPORT N
45、O. 466ATM Over DigitalFacilities Operatingat a Standard Bit Ratee.g., DS1, DS3.2-Wire Analogand DigitalAccess FacilitiesFigure 4.5 ATM Technology as a Switch - 2-Wire Analog and Digital Interfaces(PBX, Local Exchange)4.5 ATM Interworking Function (ATM Cell - PDH/SDH interworking function)ATM systems
46、 will have to interwork with narrowband systems if ATM is to be integratedinto current byte oriented networks, see Figure 4.6. The interworking function will haveto occur in both the transmission plane and the signaling plane. This document willrestrict itself to the transmission plane.InterworkingF
47、unctionPortion ofNetwork ThatOperates Using Cellsi.e., In the ATMCell DomainPDH/SDH Portionof the Network ThatOperates Using Bytes,but Not Cellsi.e., Not in the ATMDomainStandard LineRateStandard LineRateFigure 4.6 ATM Technology Operating as an Interworking Unit5. DiscussionTechnology requirements
48、for PDH/SDH oriented networks have been specified in publicstandards and ITU-T Recommendations using parameters that are applied at hardwareinterfaces and which are intended to deal with individual pieces of technology ornetwork elements, e.g. multiplexers and switches. These specifications at hardw
49、areinterfaces sometimes reflect the existence of a transport system between the hardwareinterfaces specified. This document has taken a similar approach and looks at theseparameters in the context of ATM technology operating as: a digital signal processingnetwork element; a multiplexer; a transport system; an ATM switch (digital interfacesonly); an ATM switch (digital and 2-wire interfaces); and as an interworking unitbetween the ATM cell-oriented domain and the PDH/SDH byte oriented domain.The parameters associated with these various technology d
